6 THE HOUSE FLY—DISEASE CARRIER 
Life History 
A long experience with the study of insects has in¬ 
dicated the somewhat remarkable fact that it is about 
the commonest things in general that we know the 
least. When Mr. C. L. Marlatt and the writer began 
in 1895 to work on the subject of household insects, 
we discovered that very few of the species found so 
abundantly in households were included in the museum 
collections. There would be a large series of a rare 
beetle from Brazil, but no specimens of the common 
house cockroach, for example; and when we began to 
look into the literature of their life histories we learned 
that published accounts of their transformations were 
even more scarce than the specimens in the collections. 
Doctor Hewitt (1910) calls attention to the vision of 
Sir James Crichton Browne of the aged person show¬ 
ing the wondering child the only existing specimen of 
the house fly, in the British Museum. This was in¬ 
tended as a prophecy, but it would not be surprising 
if before the recent house fly crusade began there- 
really was only one specimen of the house fly in the 
British Museum. 
With this condition of affairs existing in general, 
it is perhaps not so surprising that an exhaustive study 
of the conditions which produce house flies in numbers 
has really never been made. The life history of the 
insect was, down to 1873, mentioned in only a few old 
European works and one more modern one (Taschen- 
